In spite of numerous studies, the role of the pineal gland in human puberty remains unsettled. Factors that now are known to affect melatonin concentrations (circadian and seasonal variations, cycles of light/dark and sleep/wake activity, body size, metabolic clearance rate) may account for many of the discrepancies in published data. The purpose of the proposed studies is to examine the role of the pineal gland in normal and abnormal puberty by: (a) characterizing normal melatonin rhythms across childhood and adolescence; (b) exploring relationships between characteristics of melatonin rhythms with characteristics of rhythms of luteinizing hormone (LH) and sex steroids throughout normal puberty and in abnormal puberty; and (c) comparing parameters of melatonin rhythms in subjects with normal and abnormal puberty. Subjects will be normal children of both sexes, 6 years of age and older in various stages of puberty, and children with precocious or delayed puberty. Sleep/wake and light/dark activities will be carefully controlled for 10 days before testing. Hourly blood samples will be drawn by constant withdrawal pump for 24 hours and simultaneous urine collection will be obtained. Plasma concentrations of melatonin, LH, dehydroepiandrosterone (DHEA), testosterone (in males) and estradiol (in females) will be determined in hourly samples or in pooled aliquots of 2-4 consecutive hours. Melatonin will also be measured in urine. An LH releasing hormone (LHRH) test will assess LH response Hormones will be measured by standard radioimmunoassays. The characteristics (mesor, amplitude and acrophase) of melatonin circadian rhythms determined by simple cosinor method will be compared among pubertal groups of each sex and will be compared to urinary excretion of melatonin across all age groups. Possible relationships between melatonin circadian rhythms and the circadian rhythms of pituitary (LH), gonadal (testosterone, estradiol) and adrenal (DHEA) hormones will be investigated. These studies will also explore the relationship between the expected nighttime surges of melatonin plasma and urine with the LH response to LHRH stimulation. Finally, plasma and urinal melatonin concentrations will be correlated with body weight and body surface area. Information gained from these studies may clarify the role of the pineal gland in puberty and the data will serve as reference for studies of conditions in which melatonin rhythms might be altered (e.g. affective disorders of childhood and adolescence, pineal tumors), and for the treatment of disorders of puberty.